The present invention relates to evaluation instruments for phosphate glass dosimeters which differentially scan the glass with light radiation.
In radiophotoluminescence (RPL) radiation measuring glass dosimeters the penetration depth of ionizing radiation into the glass depends on the radiation energy (quality of the radiation).
For detecting and measuring ionizing radiation, it is known to use special phosphate glasses which form stable luminescence, or fluorescence, centers when exposed to such radiation and, after exposure, to scan the glass with ultraviolet radiation to cause those centers to produce fluorescent light whose intensity can be measured and is indicative of the ionizing radiation energy and dose. Moreover, the distribution of such luminescence centers throughout a piece of phosphate glass can vary greatly and depends on the ionizing radiation energy and direction of incidence. Thus, a comparison of the curve representing the relative measured fluorescence intensity as a function of depth in the glass in the direction of incidence of the ionizing radiation with corresponding calibration curves can be used to determine the radiation dose absorbed by human organs at a certain depth of tissue. Moreover, since the distribution of the luminescence centers in the glass clearly identifies the type of ionizing radiation, it is possible, even in the case of nonhomogeneous radiation, to distinguish between the different energy level components, such as low energy, medium, hard and high energy components, in that the curve of the emission from the luninescence centers in the vicinity of the outer glass surface at the location of incidence is determined considerably by the low energy radiation, while the curve derived from regions at a greater depth in the glass is determined to a greater extent by the high energy radiation.
As already described in German Pat. No. 1,589,856, differential scanning of the glass during evaluation can be employed to obtain information about the energy level, dose and direction of incidence of the radiation. The evaluation device for differentially scanning blocks of such glass employs a stationary slit which forms a narrow beam of light of a width of about 0.3 mm from the light produced by an ultraviolet lamp and the dosimeter glass is moved past this gap. In order to make measurements along different axes, the glass would have to be rotated manually and also inserted manually.